Steam boiler plant



y 1962 u. o. BLOMQUIST 3,043,279

STEAM BOILER PLANT Filed June 15, 1955 practically constant.

United States Patent Claims priority, application Sweden June 18, 1954 2 Claims. (Cl. 122-249) In modern steam boilers a great amount of the heat set free is absorbed directly through radiation to the circulation tubes for water, surrounding the fireplace. Usually these tubes open into one or more steam domes in which the generated steam is separated and passed on to the superheater.

Normally the combustion takes place in a fireplace chamber common to all the burners, but there are also certain types in which the fireplace, with regard to the radiation of heat, is divided into smaller fireplace chambers with vertical partition walls. Usually the fuel is supplied to the lower part of the fireplace, and therefore the combustion gases will flow through the fireplace chamber substantially in a vertical direction and in the same direction as the direction of flow of the heat-absorbing medium. When changes of load occur, the final temperature in the upper part of the fireplace will be determined by the amount of fuel supplied, in such a manner that, when the load is increased, the temperature of the departing gases is higher, while the temperature will be correspondingly lower when the load is reduced. This in turn will contribute to changes in the absorption of heat in the superheater in such a manner that lower temperature after the fireplace results in lower superheating temperature and higher gas temperature after the fireplace results in higher steam temperature.

It is important, however, in respect of the economy of a steam power plant, that it should be possible to keep the superheating temperature high Within the greatest possible range of load, and therefore various expedients have been resorted to for making this possible. For example by a combination of a convection superheater and a superheater which is directly subjected to radiation, it is possible to attain an equalisation of the variations of temperature. It is also possible to oversize the superheating surface, so that full overheating at a lower load is obtained, whereafter the overheating temperature is adjusted in a suitable manner, for example by cooling the steam, for instance by injection of water.

According to this invention a certain determined gas temperature is obtained at the egress from each particular fireplace, independently of, the number of fireplaces operated. Owing. to this the gas temperature ahead of the superheater will be constant at different loads of the boiler, whereby the steam temperature can be maintained This invention provides a possibility of supplying a uniform steam temperature over a great range of load, without it being necessary to oversize the superheater and subsequent necessities for cooling plants for the steam at higher loads. Thereby very much is gained from an economic point of view.

Apart from the above-mentioned conditions fireplaces which are substantially vertical result in great heights with regard to steam boilers. The heat load in relation to the volume of the fireplace is comparatively small with regard to ordinary fireplaces, at the same time as the course of combustion can be difiicult owing to insufiicient mixture of air and fuel, particularly in large fireplaces.

This invention relates to an improvement in a steam boiler plant, and the invention is characterized in that the combustion chamber of the boiler is divided into several smaller parallel, substantially horizontal fireplaces which are connected -to the circulation system of the boiler in such a manner that, when the load is changed, for example by disconnecting one or more fireplaces, a uniform and adequate circulation is secured, also at a natural circulation of water, owing to the disposition of the difierent fireplace elements. This fact is of great importance, particularly in the case of boilers for military purposes, where speed is necessary both with regard to starting and the possibility of varying the loads hastily. When adjusting the load, it is possible, as already mentioned, to obtain good combustion conditions, even at lower loads, by disconnecting fireplaces, owing to the fact that the remain ing groups of fireplaces then can be operated with loads which cause the most favourable combustion conditions. The different fireplaces can be provided with separate control devices for the supply of air and fuel in order to obtain as favourable a result of the combustion as possible.

By division into several smaller fireplace chambers higher heat loads are obtained, and thereby it is possible to reduce the fireplace chambers of the whole boiler, so that the consmption of material and the building space are reduced.

Furthermore, by using a combination of a greater or smaller number of standard fireplaces, it is possible to build the boiler according to the building block principle, whereby larger or smaller steam boilers with analogous combustion conditions are obtained. Thereby the disadvantages of the lar e fireplace volumes of larger steam boilers in respect of combustion are eliminated.

This invention relates to a combination of several smaller fireplaces, which are made in such a manner that they can receive an essential part of the heat released bycombustion, which heat can be used for generating steam. Furthermore the fire surfaces of these fireplaces are so fitted that such a low temperature of the departing gas is obtained that the flue gases can be conducted directly to subsequent convection surfaces, for example superheaters, without ash being deposited.

Thus, the invention must not be confused with wellknown so-called melting cyclone fireplaces in which the fire surfaces are provided with internal insulating masses serving the purpose of limiting the radiation of heat to the walls of the fireplace. The departing fiue gases from these so-called cyclone fireplaces have a very high tem perature and contain great amounts of heat, which are collected in subsequent fireplaces for final combustion. Only after it has leftthese fireplaces does the gas attain a low enough temperature so that it can be conducted to theconvection surfaces.

In the accompanying drawing an embodiment of the invention is shown. FIG. -1 'is a section through a plant according to the invention in the longitudinal direction of the fireplaces, and FIG. 2 is a section along the line IIII in FIG. 1.

Referring now to the drawing reference numeral 1 indicates fireplaces arranged in two groups with four fireplaces in each group located vertically above each other. The fireplaces 1 are cylindrical with their axes disposed horizontally. Reference numeral 2 indicates ducts for the supply of fuel, for example pulverized coal. which, in the example shown, is introduced at one end of the cylindrical fireplace. At the opposite end there is a centrally disposed outlet opening 3, and all outlet openings open into a common flue gas channel 4.

The gas flowing through the channel 4 first passes through a superheater divided into two parts 5a and 5b, thereafter through an economizer 6, and finally, via an air preheater 7, to a fan 8 from where it is conveyed to the chimney.

Combustion air is supplied by means of a fan 9 and passes through the air preheater 7 before flowing into air drums or a casing ll which may surround the fireplaces.

Patented July ll 1962 The latter are provided with openings through which air is supplied to the combustion chambers, and the said openings may be arranged in any suitable manner.

In the example shown the plant is provided with a steam dome 11 which is common to all the fireplaces, but more provided shutting-off and/or control devices, not shown I in the drawing, for fuel as well as for combustion air for each fireplace, the said devices being individually operable. The casing 19 is preferably heat-insulating, and

7 each fireplace can be made as a separate isolated unit.

From this it is obvious that when one or more of the upper fireplaces of a group is closed there will be no essential loss of heat, at the same time as the closed fireplaces are kept heated, which makes it easier to restart the operation of them. 7 e

The described. embodiment is only intended to illustrate '7 the idea of the invention and can be modified in the practice. Thus, the invention can be applied to plants for other kinds of fuel than pulverized coal, and in order to avoid deposits of ash on the tubes of the fireplaces there may be a certain interspace between the tubes, so that combustionair or flue. gases can be introduced between the tubes. The fireplaces may advantageously be made in such a manner that cyclone effect is utilized. Devices may be provided for removing ash and the like from the fireplaces, the ash being conveyed from the upper fireplaces to the lower ones, 'a single common outtake being provided at the lower end of each group or" fireplaces. The fireplaces are prefer-ably of sncha kind that the ash can be removed in molten state. v v

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A steam boiler plant characterized-by: a plurality of substantially horizontal directly superimposed substan tially cylindrical combustion chambers, the curved walls of which are formed by two laterally and symmetrically opposed groups of contiguous boiler tubes, each of which extends continuously upwardly from the bottom of the lowermost combustion chamber arcuately successively around substantially one half of the circumference of each of the superimposed substantially cylindrical combustion chambers to the top of the uppermost combustion Cl'lElIIP' ber, the upper and lower ends 'of the arcuately shaped portions of the'tubes. of one of said groups being contigu-- bus to the upper and lower ends of the'arcuately shaped 7 portions of the tubes of the other group so that the superimposed combustion chambers defined by said tubesare substantially separated from one another, each of said combustion chambers having an outlet at one end thereof and an inlet for fuel and air spaced from the outlet; means for circulating boiler fluid upwardly through all said tubes; means for independently feeding fuel and air to the inlet of each of the combustion chambers; and means at the outlet ends of the combustion chambers defining a flue gas duct common to all of said combustion chambers and into which the outlets of all said combustion chambers open so that the combustion gases flow horizontally through the combustion chambers in indirect heat exchange relation with boiler fluid flowing upwardly through the boiler tubes.

2. A steam boiler plant comprisingza plurality of substantially horizontal directly superimposed substantially cylindrical combustion chambers, the curved walls of which are defined by two laterally and symmetrically opposed groups of contiguous boiler tubes, each of which extends continuously upwardly from the bottom of the lowermost combustion chamber .arcuately and successively around substantially one half of the circumference of each of'the superimposed substantially cylindrical combustion chambers to the top of the uppermost combustion chamber, the upper and lower ends of the arcuately shaped portions ofthe tubes of one of said groups being contiguous to the upper and lower ends of the arcuately shaped portions of the tubes of the other group so that the superimposed combustion chambers defined by said tubes are substantially separated from one another, each of said combustion chambers having an inlet at one end thereof and an outlet at its opposite end; a common steam drum with which the upper ends'of all of the boiler tubes connect; header means at the bottom of the lowermost combustion chamber with which the lower ends of the boiler tubes connect; a down'comer connecting the steam drum with said'header means so that boiler fluid circulating in the system flows upwardly through all of the boiler tubes; means at said first designated ends of the superimposed combustion chambers for independently feeding fuel and air to each of the combustion chambers; and means at the second designated ends of the combustion chambers defining a flue gas duct common to all of the combustion chambers and into which the outlets of all of said combustion chambers open, so that the combustion gases flow horizontally through the combustion chambers in indirect heat exchange relation with 4 the boiler fluid flowing upwardly through the boiler tubes.

References Cited in the file of this patent UNITED STATES PATENTS Belgium Jan. 15, 1953 

